Measure the windows where you want to install the Grisham window bars, using a tape measure. If you are installing Grisham window bars on all windows, ensure one set has a quick-release mechanism so you can escape in the event of a fire or emergency.
Mark the end points where the bars will sit over the window.
Drill the points, making sure the depth is sufficient for the screws. Make sure you are using security screws and not regular screws. The heads of security screws lock into the material they are being screwed into; this makes them difficult to remove and acts as an additional deterrent against tampering.
Place the Grisham window bars over the window, ensuring the ends line up with the drill holes.
Insert the screws into the window bars and drill holes and tighten to secure the window bars in place.